This invention relates to 2-trifluoromethylalkanesulfonanilides substituted in the para position by alkylthio, alkylsulfinyl or alkylsulfonyl groups and to agriculturally acceptable salts thereof. The compounds of the invention are active plant growth modifying agents. The invention also relates to plant growth modifying compositions comprising the compounds of the invention dispersed in agriculturally acceptable extending media and to the use of the compounds to modify the growth of higher plants. Methods for preparing the compounds and intermediates in their preparation are also included.
Plant growth modification as defined herein consists of all deviations from natural development, for example, defoliation, stimulation, stunting, inhibition, desiccation, tillering, and even death. This plant growth modifying activity is generally observed as the compounds of the invention begin to interfere with certain processes within the plant. If vital processes are affected, the plant will die if treated with a sufficient dose of the compound and the compound can be termed a herbicide relative to that plant. If the plant is a weed, the compound can be used to control or kill it and this is particularly valuable when a compound controls or kills a weed at an application rate that has little or no effect on a crop plant. I.e., it can serve as a selective herbicide to control or kill the weed in the presence of that crop. On the other hand, the growth of desirable plants can sometimes be modified beneficially, e.g., to suppress undesirable growth or to improve the quantity or quality of the harvest from the plant or to serve as a harvest aid. Such beneficial modifications can be termed plant growth regulation.
The compounds of the present invention are broadly active as plant growth modifiers. As such they are plant growth regulators and herbicides and, as will be seen, frequently also serve as selective herbicides.
Both haloalkylsulfonamido-substituted and methylsulfonamido-substituted aromatic compounds have been known heretofore, as have certain uses for these compounds. Thus, U.S. Pat. No. 3,639,474 discloses trifluoromethanesulfonanilides, including such compounds with trifluoromethyl, methylthio, methylsulfinyl and methylsulfonyl substituents, to be useful as herbicides. French Pat. No. 1,188,591 includes disclosures of two classes of compounds, i.e., haloalkylsulfonanilides and haloalkylsulfonamidodiphenyl compounds in which the rings are bonded directly or are linked by various groups including sulfonyl, sulfinyl and thio groups. The areas of utility disclosed by the French patent include activity against textile material parasites as well as antibacterial and anti-mildew activity. Herbicidal activity is not disclosed in that patent however. British Pat. No. 971,219 discloses alkanesulfonanilides containing both chlorine and nitro ring substituents to have herbicidal activity.
U.S. Pat. No. 3,996,277 discloses that 4-methylthio-2-trifluoromethylmethanesulfonanilides (and the methylsulfinyl and methylsulfonyl derivatives thereof) have plant growth regulating activity, and that they are particularly valuable in controlling established rhizomatous johnsongrass (Sorghum halepense (L. Perse.)), a stubborn weed pest, particularly in the southern United States. Such compounds have, in fact, the particularly valuable selective herbicidal property of controlling rhizomatous johnsongrass at application rates tolerated by cotton. Thus they can be used to control rhizomatous johnsongrass selectively in cotton fields, a unique and extremely valuable characteristic.
The compounds of the present invention, which are structurally similar to those of U.S. Pat. No. 3,996,277, also have this selective activity and in addition have further advantages as selective herbicides relative to degree and kind of activity and/or tolerance with respect to other crops and as plant growth regulators. For example, compounds of the invention are effective in increasing the sucrose yield in sugar cane, in retarding the growth of grass, in controlling tobacco sucker growth and in increasing the sweetness to acidity ratio of citrus.